Answer:Because she's insane? And very ill. And dangerous. A pure bred psychopath. She got off screwing with him, his head. She has a degree in effing with you. Beth was just a bonus. Unlucky. Collateral damage. Unfortunate. Catherine was, is a clinical psychopath. She had no reason. Or it was fun for her. She was one twisted broad. An evil dame. (IMHO).